/*
 * Copyright 2002-2018 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.expression.spel.support;

import org.springframework.core.convert.ConversionException;
import org.springframework.core.convert.ConversionService;
import org.springframework.core.convert.TypeDescriptor;
import org.springframework.core.convert.support.DefaultConversionService;
import org.springframework.expression.TypeConverter;
import org.springframework.expression.spel.SpelEvaluationException;
import org.springframework.expression.spel.SpelMessage;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;

/**
 * Default implementation of the {@link TypeConverter} interface,
 * delegating to a core Spring {@link ConversionService}.
 *
 * @author Juergen Hoeller
 * @author Andy Clement
 * @see org.springframework.core.convert.ConversionService
 * @since 3.0
 */
public class StandardTypeConverter implements TypeConverter {

    private final ConversionService conversionService;


    /**
     * Create a StandardTypeConverter for the default ConversionService.
     *
     * @see DefaultConversionService#getSharedInstance()
     */
    public StandardTypeConverter() {
        this.conversionService = DefaultConversionService.getSharedInstance();
    }

    /**
     * Create a StandardTypeConverter for the given ConversionService.
     *
     * @param conversionService the ConversionService to delegate to
     */
    public StandardTypeConverter(ConversionService conversionService) {
        Assert.notNull(conversionService, "ConversionService must not be null");
        this.conversionService = conversionService;
    }


    @Override
    public boolean canConvert(@Nullable TypeDescriptor sourceType, TypeDescriptor targetType) {
        return this.conversionService.canConvert(sourceType, targetType);
    }

    @Override
    @Nullable
    public Object convertValue(@Nullable Object value, @Nullable TypeDescriptor sourceType, TypeDescriptor targetType) {
        try {
            return this.conversionService.convert(value, sourceType, targetType);
        } catch (ConversionException ex) {
            throw new SpelEvaluationException(ex, SpelMessage.TYPE_CONVERSION_ERROR,
                    (sourceType != null ? sourceType.toString() : (value != null ? value.getClass().getName() : "null")),
                    targetType.toString());
        }
    }

}
